Circuit breaker contact means



Jan. 7, 1941. J. M. CUMMING ETAL CIRCUIT BREAKER CONTACT MEANS Filed Nov. 1, 1938 2 Sheets-Sheet l I INVENTORS /Zme s%( WITNESSES:

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CIRCUIT BREAKER CONTACT MEANS Filed NOV. 1, 1958 2 Sheets-Sheet 2 WITNESSES: |NVENTOR5 java: 9

Z/ /ZM/6/v A? 1 BT Z /W ATTORNEY' Patented Jan. 7, 1941 UNITED STATES PATENT OFFICE CIRCUIT BREAKER CONTACT MEANS Application November 1, 1938, Serial No. 238,128

9 Claims.

The invention relates to circuit interrupters in general and more particularly to the contact means of heavy-duty circuit breakers designed to interrupt relatively large amounts of power.

In previous circuit breaker structures, particularly those in which are extinguishing structures are associated with the stationary contacts, considerable difiiculties have been experienced in obtaining access to the stationary contact means and in removing the same for inspection, repair or replacement purposes. In most instances it is necessary to dismantle a large number of parts; and it is very diiiicult to return the parts to their original positions without disturbing the correct adjustment and alignment of these and other related parts. The stationary contact fingers are usually mounted on pivot pins within a supporting casting which is rigidly secured to other parts of the breaker structure. The contact fingers are biased about their pivots toward the movable contact by spring means disposed in recesses in the casting. To removed the contact fingers, it is necessary to drive the pivot pins out of their bearing recesses, dismantle the arc extinguishing structure and the shunt conductors, and work the contact fingers out of their recesses. The pivot pins often become bent and wedged or jammed in their bearing holes and it is very difiicult to extract the same. This fact, coupled with the inaccessibility of the parts and the complicated shape of the supporting casting, makes it difficult to remove, and to restore the stationary contact fingers.

An object of the invention is the provision of a circuit breaker embodying improved contact means and mounting means therefor which permits the stationary contacts to be very easily removed without dismantling other related parts, and which permits the return of the contacts to their original positions without disturbing the proper adjustment and alignment of the related parts.

Another object of the invention is the provision of a circuit interrupter in which the stationary contact means are mounted as a unit and readily removable from the remaining structure of the interrupter.

Another object of t e invention is the provision of a circuit interrupter having pivotally mounted stationary contact fingers and biasing springs for the fingers, all of which are mounted as a unit on a supporting means which is readily removable as a unit'from the remaining structure of the circuit interrupter.

Another object of the invention is the provision of a circuit interrupter embodying a simple supporting structure for the stationary contact means consisting of two separable sections, one section of which is rigidly secured to other fixed structure of the interrupter, and the other section of which is removably mounted on the fixed section and carries the stationary contact means as a unit whereby the stationary contact means is readily removable from the interrupter.

Another object of the invention is the provision of a circuit interrupter in which the stationary finger contacts, their pivot pins, the flexible shunt secured to the finger contacts, and the biasing springs for the contacts are all mounted as a unit on a removable section of a two-part separable supporting structure so as to be easily removable as a unit from the fixed part of the structure Without dismantling any of the remaining structure of the interrupter.

Another object of the invention is the provision of a circuit interrupter as previously described in which the fixed section of the two-part contact supporting structure is recessed to accommodate the stationary contact means, and is rigidly secured to the terminal stud of the interrupter and supports the are extinguishing structure.

Another object of the invention is the provision of a circuit breaker embodying an improved movable bridging contact member and means for securing the contact member to the end of the lift rod, which provides for easy vertical adjustment of the contact member on the rod.

Another object of the invention is the provision of improved circuit breaker contact means that is simple, compact, easily accessible, and inexpensive to manufacture.

The novel features that are considered characteristic of the invention are set forth in particular in the appended claims. The invention itself, however, both as to structure and operation, together with additional objects and advantages thereof, will be best understood from the following detailed description of one embodiment thereof when read in conjunction with the accompanying drawings, in which:

Figure 1 is a vertical sectional View of a circuit breaker embodying the improved contact means of the present invention;

Fig. 2 is an enlarged fragmentary elevational view, partly in section, of the contact means of the breaker;

Fig. 3 is an enlarged end elevational view, partly in section, of the contact means;

Fig. 4 is an enlarged perspective view of the fixed contact foot section of the two-part supporting structure for the stationary contact means;

Fig. 5 is an enlarged perspective view of the removable cover box section of the contact supporting structure with t e stationary contact ieans mounted thereon; and

Fi 6 is an enlarged fragmentary horizontal sectional view of the movable contact means taken substantially on the line VIVI of Fig. 2.

Referring to Fig. l of the drawings, the circuit breaker shown comprises a liquid-tight metal tank 9 having a metal cover I I removably mounted thereon by a plurality of bolts |3 which extend through the rim of the cover I and engage threaded openings provided in an outwardly extending flange |5 of the tank 9.

A pair of conventional insulating terminal bushings H are mounted in spaced relation on the cover H by means of the mounting sleeves l9 and a plurality of cap screws 2|. The bushings I! extend through the cover into the interior of the tank 9 and serve to insulate and support a pair of terminal studs 23 and 25 which extend through the interior of the bushings IT and are insulated from the cover H and tank 9 thereby. The upper ends of the terminal studs 23 and 25 extend beyond the ends of the bushings I1 and are provided with terminal nuts 29 or any other suitable terminal connections for connecting the circuit breaker to the electrical circuit which it is adapted to control.

A pair of spaced stationary contact assemblages indicated generally at 3| are secured to the lower ends of the terminal studs 23 and 25 within the tank 9. Removably mounted within each of the contact assemblages 3| are a pair of opposed spring-pressed finger contacts 33 (Fig. 3, only one being shown), each set forming one of the stationary contact means of the breaker. A pair of arc extinguishing structures 34 are secured to the contact assemblages 3| for the purpose of extinguishing arcs formed during interruption of the circuit controlled by the breaker.

A movable bridging contact member 35 in the form of a U-shaped bridging bar is disposed within the tank 9 for bridging the stationary contact means of the breaker. The movable bridging member 35 is secured intermediate its ends to the lower end of a vertically movable operating lift rod 31, which is preferably formed of a strong insulating material. The upper end of the lift rod 3'5 is connected to a suitable circuit breaker operating mechanism (not shown) which is operable to move the bridging contact member 35 upwardly to closed circuit position, as shown in full lines in Fig. 1, in bridging engagement with the two sets of finger contacts 3|, and which is also operable to move the bridging contact member 35 downwardly to open circuit position away from the stationary contact means, as indicated by the dotted lines in Fig. 1. The circuit breaker mechanism may be of any suitable type, but is preferably of the type fully described in the copending application of John B. MacNeill and John W. May, Serial No. 79,670, filed May 14, 1936, and assigned to the assignee of the present invention now Patent No. 2,144,504 issued January 17, 1939.

The tank 9 is filled with a body of insulating liquid, such as oil, or the like, substantially to a level indicated at 39 in Fig. 1 slightly above the stationary contact assemblages 3|. The body of insulating liquid serves to insulate the live parts of the circuit breaker from the metal tank 9, and

also assists in extinguishing the arcs formed during circuit interruption.

Each of the stationary contact assemblages 3| comprises a supporting structure consisting of a pair of separable sections or castings 4| and 43, 5 which are preferably cast of conducting material, such as copper or a suitable alloy of copper. Referring to Figs. 2, 3 and 4 of the drawings, the contact foot section 4| of the supporting structure is provided with a generally rectangular chamber 45 (Fig. 4) which is open at the bottom and also at one side of the casting 4| for receiving the stationary contact means. The upper end of the contact foot section 4| is formed to provide a split clamp 41 which is internally threaded and adapted to engage the threaded lower end of its corresponding terminal stud 23 or 25 to secure the contact foot section in mounted position on the lower end of its terminal stud. A bolt 49 (Fig. 2) passes through the split ends of the clamp 41 for drawing the ends together to securely clamp the contact foot section 4| to the end of its corresponding terminal stud.

The upper wall of the contact foot section 4| is provided with a pair of cavities 5| (Fig. 4) adjoining each side wall 50, and these cavities are open at the open side of the casting 4|. The opposite upper sides of the top of the casting 4| are machined down along the lines 53, 55 by a single machine operation into the upper ends of the cavities 5| to provide openings between the side walls 50 and the top portion 52 of the casting 4| so that the cavities 5| form slots or recesses open at the top and sides for receiving a pair of flexible shunt conductors connected to the finger contacts 33 as will be hereinafter described. The provision of the casting 4| with the cavities 5|, as previously described, thus permits the shunt conductor receiving slots to be formed by a single machining operation, thus eliminating one or more additional machining operations to provide these openings.

The opposite sides of the contact foot section 4| are provided with horizontal projections 51 (only one appearing in Fig. 4), each having a pair of bolt receiving openings 58 formed therein. The arc extinguishing structures 34 are secured to the contact foot sections 4| against the bottom edges thereof by means of a plurality of bolts 59 which pass through the openings 58 in the 50 horizontal projections 51 and are secured by nuts 6| threaded on the upper ends thereof. Suitable insulating sleeves 63 and 65, and insulating washers 61 (Fig. 3) are provided to insulate the bolts 59 from the contact foot sections 4|.

The arc extinguishing structure 34 is preferably of the type fully shown and described in Patent No. 2,039,054 issued to S. H. Boden and S. T. Schofield, April 28, 1936, and assigned to the assignee of the present invention. Briefly the arc extinguishing structure comprises a. stack of slotted plates arranged between the pair of end plates 69 of insulating material, the plates being held together by the bolts 59 about which are disposed sleeves of insulating material. The plates of the arc extinguishing structure 34 are provided with aligned vertical openings through which the vertical contact portions ll of the bridging contact bar 35 is moved into bridging engagement with the finger contacts 33. The are extinguishing structures 34 are also provided with slots 13 for accommodating the horizontal portions of the bridging contact bar 35 when it is moved to closed circuit position, as shown in Fig. 2.

Mounted in an opening 15 (Fig. 4) formed in 75 the lower end of the back wall 11 of each of the contact foot sections 4| is an arcing horn 19 (Fig. ,2) to which the are drawn by the movable contact bridging bar 35 is transferred when the bridging contact bar has been moved downwardly a predetermined amount. The arcing horns 19 are secured to the contact foot sections 4| by means of a pair of bolts or cap screws 8| which engage threaded openings provided therefor in the back wall of the contact foot section 4|.

The other section 43 of the contact supporting structure is also preferably cast of suitable conducting material and this section forms a cover box for the chambered contact foot section 4|. The cover box section 43 is remo-vably mounted on the face 83 of the open side of the contact foot section 4| by means of a plurality of bolts 85 (Fig. 3) which pass through openings provided in the wall 81 of the cover box section 43 and engage threaded openings 89 (Fig. 4) formed in the contact foot section 4|.

Projecting inwardly from the wall 81 of the cover box section 43 and formed integral there with is a yoke 9| having a pair of legs 93 and a bridging portion (Fig. 5), the yoke 9| and the Wall 81 serving to support the stationary contact means of the breaker.

Each pair of finger contacts 33 are pivotally mounted in spaced opposed relation on the cover box section 43 by means of a pair of parallel pivot pins 91 which are transversely supported by the cover box section 43 between the wall 81 and the bridge 95 of the yoke 9|. The ends of the finger contact supporting pins 91 project through bearing openings provided therefor in the bridge 95 of the yoke 9| and in the wall 81 of the cover box section 43, and are retained in mounted'position on the cover box section 43 by means of cotter pins 99.

Each of the finger contacts 33 comprises a generally rectangular block of conducting material which is provided adjacent its upper end with a transverse pivot opening |0| (Fig. 3) which extends transversely through the block from edge 'to edge and engages the corresponding pivot pin 91 carried by the cover box section 43. The pivot openings |0I of the contact blocks 33 are considerably wider than the diameter of the pivot pin 91, as shown in Fig. 3, so that the finger contacts 33 can move bodily a limited amount toward and away from each other and can also swivel a limited amount on the pivot pins 91 in order to automatically align with the contact surf-aces of the vertical contact portions 1| of the movable bridging contact member 35. The finger contacts 33 are thus mounted on the cover box section 43 for pivotal movement toward the contact faces of the bridging member 35 and also for limited floating and/0r swiveling movement normal to their pivot axis in order to automatically align with the contact surfaces of the bridging member 35.

The finger contacts 33 are biased towards each "other to engage the contact surfaces of the bridgject through openings I01 formed in the legs 93 of the yoke, and have sleeves I08 secured to the outer ends thereof for limiting movement of the lower ends of the finger contacts 33 towards each other. The openings I01 are of greater diameter than the studs I05 so as to permit free pivotal as well as limited floating and swiveling movement of the contacts 33 on the pivot pins 91. The lower ends of the finger contacts 33 are rounded and provided with inserts I09 of suitable arcresisting material. Similarly, the upper contact ends of the movable contact bridging bar 35 are provided with are resisting inserts I I I, the edges of which are rounded to facilitate entrance of the ends of the bridging bar between the finger contacts 33.

A pair of flexible shunt conductors 3 formed of thin laminations of copper strip are rigidly secured at their lower ends to the back of the finger contacts 33. The upper ends of the flexible shunt conductor I I3 are capped by a pair of relatively stifi U-shaped strips II5 of conducting material, and suitable openings 1 are formed through the upper ends of the shunts and the caps for securing the free ends of the shunt conductors to the upper end of the contact foot section 4|.

From the above description it will be seen that the finger contacts 33, the flexible shunt conductors |I3 secured thereto, and the biasing springs I03 for the finger contacts are all mounted on the cover box section 43 for removal therewith as a unit from the fixed contact foot section 4|. The flexible shunt conductors ||3 extend upwardly through the slots 5| in the fixed section 4|, and their upper ends are removably secured to the sides of the upper end of the contact foot section 4| by a pair of cap screws ||9 which pass through the openings I I 1 in the shunt conductors H3 and engage in threaded openings provided in the upper end portion 52 of the contact foot section 4|. To remove either pair of the stationary contact means, it is only necessary to remove the screws I I9 which connect the flexible shunt conductors M3 to the fixed section 4| and to remove the bolts 85 which secure the cover box section 43 to the contact foot section 4|. The contacts are then removed simply by withdrawing the cover box section 43 from the fixed contact foot section 4|. The finger contacts 33 and biasing springs I03 and flexible shunt conductors 3 are all removable as a unit with the cover box section 43. The stationary contact means of the circuit breaker may thus be readily removed from the other fixed structure of the breaker for inspection, repair or replacement purposes without dismantling the are extinguishing structure or other related fixed parts, and may also be easily returned to their original positions without disturbing the alignment or ad-- justment of the arc extinguishing structure and other related fixed parts.

To return the contact means to mounted position, the cover box section. 43 is slipped into mounted position on the contact foot section 4| and this places the finger contacts 33 in proper position in the chamber 45 of the contact foot section 4|. The cover box section 43 is then secured in place by tightening the bolts 85. As the cover box section 43 is returned to mounted position on the contact foot portion. 4| the flexible shunt conductors ||3 slip endwise into the slots 5| in their proper position and their upper ends are then secured to the upper portion 52 of the contact foot section by inserting and tightening the cap screws H9.

The movable bridging contact member 35 of the circuit breaker is constructed of two fiat bars I2I and I23 (Fig. 6) of conducting material such as copper or the like which are secured together face to face and formed to provide a substantially circular opening I25 at the center of the member. The opening I25 is threaded and engages a threaded metal rod end I21 which is secured to the lower end of the lift rod 31. The metal rod end I21 is secured to the lower end of the lift rod 31 in any suitable manner, for example, by having one or more grooves I29 press-fitted into the lower section of the lift rod. A pair of members I3I of insulating material are bolted to the lift rod 31 by a pair of bolts I33, the members I3I being provided with a cylindrical recess which is inter-engaged with an outwardly extending flange formed on the upper end of the metal rod end I21 as shown in Fig. 2. These insulating members serve as an insulating barrier between the two sets of stationary contacts and the arcs drawn therefrom.

The sections of the bars I2I and I23 on opposite sides of the cylindrical opening I25 are slightly ofiset as indicated at I35 (Fig. 6) to provide slight spaces between the sections of the bars I2I and I23 on either side of the circular opening I25. A pair of bolts I31 extend transversely through the offset sections I35 of the bars on either side of the circular opening I25 for drawing the offset sections toward one an other to tightly clamp the movable contact bridging member 35 on the metal rod end I21 of the lift rod 31. The previously described construction of the movable bridging contact member and its mounting on the end of the lift rod provides for vertical adjustment of the movable contact bridging member 35 relative to the pivoted finger contacts 33 and the lift rod 31. To adjust the vertical position of the bridging member it is only necessary to loosen the bolts I31 and rotate the bridging member 35 to raise or lower the same on the threaded rod end I21. After the member 35 has been moved to the desired adjusted position the bolts I31 are tightened. The adjustable construction is simple, compact, small in size and weight, and convenient to manipulate for vertically adjusting the position of the movable bridging contact member.

A stationary contact means and mounting arrangement embodying some features which are somewhat similar to the present invention are disclosed and claimed in the copending application of James M. Cumming and Raymond H. Leitzel, Serial No. 238,832, filed November 2, 1939, and assigned to the assignee of the present invention.

While the invention has been disclosed in accordance with the provisions of the patent statutes, it is to be understood that various changes in the structural details thereof may be made without departing from the spirit of the invention. It is desired, therefore, that the appended claims be given the broadest reasonable construction that is permissible in the light of the prior art.

We claim as our invention:

1. In a circuit interrupter, a contact member movable to open and to closed circuit position, stationary contact means comprising a pair of opposed pivoted finger contacts disposed to engage the sides of said movable contact member when said movable contact member is in closed circuit position, spring means for biasing said finger contacts towards each other to provide contact pressure when the interrupter is closed, a supporting and enclosing structure for said stationary contact means comprising a two-part separable housing, one part of said housing having means rigidly securing it to a fixed structure of the interrupter and having a chamber for accommodating said stationary contact means open at one side of the part to permit insertion and removal of the stationary contact means, the other part of said housing being removably mounted on the open side of the fixed part of the housing by one or more fastening screws and having means for supporting said stationary contact means, said stationary contact means being removable by the removal of said removable part of the housing while the fixed part remains rigidly secured to the fixed structure of the interrupter and without loosening said securing means.

2. In a circuit interrupter, a contact member movable to open and to closed circuit position, stationary contact means comprising a pair of opposed finger contacts disposed to engage the sides of said movable contact member when said movable contact member is in closed circuit position, said finger contacts being movable toward and away from each other, spring means for biasing said finger contacts towards each other to provide contact pressure when the interrupter is closed, a supporting and enclosing structure for said stationary contact means comprising a two-part separable housing, one part of said housing having means rigidly securing it to a fixed structure of the interrupter and having a chamber for accommodating said stationary contact means open at one side of the part to permit insertion and removal of the stationary contact means through the open side, the other part of said housing being removably mounted on the open side of the fixed part of the housing, and said stationary contact means including said finger contacts and said spring means being mounted on said removable part of the housing for removal therewith as a unit from the fixed housing part without loosening said securing means.

3. In a circuit breaker having a plurality of terminals, a contact member movable to open and to closed circuit position, stationary contact means comprising a pair of opposed pivotally mounted finger contacts disposed to engage the sides of said movable contact member when said movable contact member is in closed circuit position, spring means for biasing said finger contacts towards each other to provide contact pressure when the breaker is closed, a flexible shunt conductor secured at one end to each finger contact, a supporting and enclosing structure for said stationary contact means comprising a twopart separable housing, one part of said housing being rigidly secured to a terminal of the breaker and having a chamber for accommodating said stationary contact means and an open side through which said stationary contact means may be inserted and removed, the other part of said housing being removably mounted on the fixed part over the open side thereof by one or more fastening screws, said stationary contact means including said pivoted finger contacts, said spring means and said flexible shunt conductors being mounted on the removable part of the housing for removal therewith as a unit from the fixed part which remains rigidly secured to said terminal.

4. In a circuit breaker, a movable contact member, stationary contact means comprising a pair of opposed pivoted finger contacts for engaging the sides of said movable contact member, said finger contacts being loosely pivoted for movement toward and away from each other and for limited self-aligning movement to automatically align with the movable contact member when the breaker is closed, spring means for biasing said finger contacts towards each other to provide contact pressure when the breaker is closed, a flexible shunt conductor secured at one end to each finger contact, a supporting and enclosing structure for said stationary contact means comprising a two-part separable housing, one part of said housing being rigidly secured to a fixed structure of the breaker and having a chamber for accommodating said stationary contact means and an open side to permit insertion and removal of said stationary contact means, the other part of said housing being removably mounted on the fixed part over the open side by one or more fastening screws, and said stationary contact means including said pivoted finger contacts and said spring means being mounted on the removable part of the housing for removal therewith as a unit from the fixed part which remains rigidly secured to the fixed structure of the interrupter.

5. In a circuit interrupter, a movable contact member, stationary contact means comprising at least one pivoted finger contact for engaging the side of said movable contact member, a flexible shunt conductor secured at one end to said finger contact, spring means for biasing said finger contact into pressure engagement with said movable contact, a supporting and enclosing housing for said stationary contact means comprising a pair of separable sections one of which is rigidly secured to a fixed structure of the interrupter and has a chamber for accommodating said finger contact and its spring means and has a recess for accommodating said flexible shunt conductor through which said flexible shunt conductor extends and an open side to permit insertion and removal of said stationary contact means, the other of said sections being removably mounted on the fixed section over the open side by one .or more fastening screws, said finger contact and its flexible shunt conductor and said spring means being mounted on said removable section for removal therewith as a unit from said fixed section which remains rigidly secured to the fixed structure of the interrupter.

6. In a circuit interrupter, a movable contact member for opening and closing the circuit, stationary contact means comprising a pair of opposed pivoted finger contacts for engaging the sides of said movable contact member, spring means for biasing said finger contacts into pressure engagement with said movable contact member, a supporting and enclosing structure for said stationary contact means comprising a pair of separable sections, one of said sections being secured to a terminal of the breaker and having a chamber for accommodating said stationary contact means open at one end of said section to permit movement of said movable contact member into engagement with said finger contacts and open at a side of said section to receive said stationary contact means, an arc extinguishing structure having a plurality of parts and means securing said arc extinguishing structure and the parts thereof to the fixed section adjacent the open end, the other of said pair of sections being removably mounted on the open side of said fixed section, said finger contacts and said spring means being mounted on said removable section for removal therewith as a unit from said fixed section which remains fixed and secured to the arc extinguishing structure and terminal.

7. In a circuit interrupter, a pair of spaced stationary contact means each comprising a pair of opposed pivotally mounted? finger contacts biased towards each other, a bridging member movable into bridging engagement with said contacts, a lift rod for moving said bridging member into and out of engagement with said contacts, and means for adjustably mounting said bridging member on said lift rod to permit adjustment of the position of said bridging member relative to said contacts, said means comprising a threaded portion on said lift rod, a pair of opposed internally threaded sections on said bridging member adjacent the center thereof forming a substantially circular threaded opening for engaging the threaded portion of said lift rod, and means for drawing said sections towards each other into tight clamping engagement with the threaded portion of the lift rod.

8. In a circuit breaker, a pair of spaced stationary contacts, a movable bridging member for bridging said contacts, a movable lift rod for moving said bridging member into and out of engagement with said contacts, said lift rod having a threaded portion and said bridging member having opposed internally threaded sections adjacent its center forming a substantially circular threaded opening for engaging the threaded portion of said lift rod to permit adjustment of said bridging member relative to said contacts and lift rod, and bolt means for drawing said sections toward one another into tight clamping engagement with the threaded portion of the lift rod.

9. In a circuit breaker, a pair of spaced contacts, a movable bridging member for bridging said contacts, a movable lift rod for moving said bridging member into and out of engagement with said contacts, said bridging member comprising a pair of flat bars of conducting material formed to provide a substantially circular threaded hole adjacent the center for engaging a threaded portion of the lift rod to provide for adjustment of said bridging member on said lift rod, said bars being slightly spaced apart on either side of said hole, and bolt means extending transversely through said bars on both sides of said hole for tightly clamping said bridging member to the threaded portion of said lift rod.

JAMES M. CUMMING. ALLAN W. HILL. 

